This monster sound is more of a roar or snarl. It's really just me going, "grrrrrrr" and "Rarrrr!" and all kinds of other annoying noises! Then I run it through Audacity and lower the pitch on each one three or four steps, slap on some gverb, and overlap them. The deeper sounds also get about a 50% bass boost. To give it a breathy sound, I also made some hissing-cat noises into the mic. (Ever think that we sound-editing buffs must look pretty ridiculous sitting at a computer making these noises?)